There is an ongoing need for solid state circuits adapted to operate at higher and higher frequencies, including microwave frequencies. As used herein, the term “microwave” is intended to refer to frequencies at or above about 200 mega-Hertz, for example in the range of 300 Mhz to 3 GHz. Various transistor structures have been created that are capable of providing gain in such frequency ranges. A LDMOS (Lateral Diffused Metal Oxide Semiconductor) transistor is an example of such a transistor structure.
At high frequencies parasitic coupling between conductive portions of the metallization structure of transistor structures can limit performance. One way of decreasing parasitic coupling is through the use of dielectric material with a lower dielectric constant within one or more layers of the metallization structure. Such dielectric materials may be called low-k dielectrics and typically have a dielectric constant k in the range of 2.5 to 4.1. However, such low-k dielectric materials may be mechanically sensitive and more difficult to process.
Therefore, further improvements to reduce parasitic coupling in semiconductor devices for use at higher frequencies are desirable.